1. Unless I missed detailed pictures, no one responding to this thread, even me, cannot tell you what your car really needs.
2. If someone [credible] is saying you need a 3 step correction your paint must be in really bad shape.
3. I'm only a detailing hobbyist but I'd be hard pressed to do a 3 step correction on an E-class sized car in 9 hours and do a good job (clean wheels, body wash incl. jambs, body decon, body wash, clay, corr. step 1, corr. step 2, corr. step 3, body wash. Do I understand that this guy isn't going to apply any LSP, only correct the paint? If that's the case you'll want a ceramic coating or a quality paint sealant (don't listen to the Nu Finish dinosaurs). Not saying this guy can't do it but it's a big job.
4. Swirls in your paint come almost exclusively from your wash process. If you do it right (two bucket method, microfiber mitts, dedicated mitts (wheels only, flats only, sides only), touchless drying whenever practical) you should be able to go LITERALLY YEARS before noticeable swirls appear. I'd also refrain from claying your car unless you need to polish because clay is mildly abrasive and WILL mar your paint. Instead of claying, your twice per year decontamination should be chemical (iron remover, tar remover) and NOT mechanical (clay).